The invention relates generally to disk storage systems for controlling arrays of disk drives, and in particular, to a method for obtaining information, such as status information, about groups of the disk drives.
In a typical high speed disk array system, such as that manufactured by EMC Corporation under the name Symmetrix.RTM., the disk array system receives, from connected host computers, input/output (I/O) requests through an interconnection channel. In an open-systems environment, a typical channel is a SCSI channel, and the I/O requests are typically composed of read and write operations. Traditionally, these disk storage systems were passive storage systems making large amounts of magnetic disk storage available to The host computers connected to them. As the speed of the interconnections between the host and the disk drive arrays has increased, and as the arrays themselves, which can be controlled by a single disk controller, have both grown in size and become more intelligent, more information is available about the array and more information can be received and processed at the host computers, as well as at the disk drive controller, about the status of the system.
In those systems wherein a plurality of host computers connect to a single disk drive controller (the Symmetrix.RTM. controller for example) over a SCSI bus, a host has the ability to send a SCSI Inquiry command to the disk drive controller to obtain information about the devices to which that host has access. However, as graphical user interfaces (GUI's) develop for greater control of the disk drive system, as a whole, from a host computer, it becomes increasingly important for the controlling host computer to have as much information available to it as possible. Nevertheless, protocols, as the SCSI protocol, do not provide a mechanism for obtaining information about disk drives which are not available to the inquiring computer itself.
In particular, some mechanism is needed, in a SCSI environment, which enables a host computer to make inquiries of all or a group of disk drives, not all of which are normally accessible to the host. No mechanism exists in the SCSI command library, which is well defined, to perform that function. The closest; command is a standard Inquiry command, in which the host computer can obtain information about a designated disk drive to which it has access.